The fascinating story of the mineral from a single hill...

Blue John is a mineral native to just one cavern system, beneath just one hill, overlooking the picture-postcard village of Castleton, in the High Peak of Derbyshire. It is a type of fluorspar, prized for the patterns or 'veins' of rich purples creamy whites and iron reds emanating from different pockets of the same hillside. Its use as ornamental material goes back centuries, with its heyday in the late 18th century when it adorned fireplaces and drawing rooms of the great country houses.

Clevedon Salerooms valuer Mark Huddleston is well-versed in dealing with Blue John, having sold a number of collections in his two decades in the business, learning a little from experts in Castleton along the way. If you are fortunate enough to own a piece of this captivating stuff, it could be worth hundreds or even thousands of pounds, and Mark would love to hear from you...